Wake induced voltage in LCLS-II: LTU + undulator (existing) HXR: LTU--Cu round pipe, a= 1.6 cm, L= 300 m; und.—Al flat pipe, 130 m (active length) (new) SXR: LTU—Cu or SS, a= 1.6 cm, L= 350 m; und.—Al flat pipe, 80 m (active length) Bunch distribution uniform with I= 1 kA; nominal Q= 100 pC (z= 8 m, ell= 30 m), high Q= 300 pC (z= 25 m, ell= 90 m) Take E= 4 GeV Relative induced energy variation for uniform bunch: w= (eIL/cE)W(s’)ds’

LTU resistive wall wake, round pipe, a= 1 LTU resistive wall wake, round pipe, a= 1.6 cm; Cu (blue), SS (red); characteristic distance s0= (2a2/Z0)1/3; s0= 28 m (Cu), 99 m (SS); W here is scaled by Z0c/a2

LTU: induced relative energy for uniform bunch distribution LTU: induced relative energy for uniform bunch distribution. For Q= 100 pC, head of bunch is at s= 0, tail at s= 30 m; for Q= 300 pC, head of bunch is at s= 0, tail at s= 90 m

undulator: induced energy variation for uniform bunch undulator: induced energy variation for uniform bunch. HXR (blue), SXR (red)

LTU+undulator: induced relative energy for uniform bunch distribution after undulator. HXR (blue), SXR (Cu, red); dashes give result after LTU

LTU+undulator: induced relative energy for uniform bunch distribution after undulator. HXR (blue), SXR (Cu, red), SXR (SS, green); dashes give result after LTU